Molten metal pump



April @1937. w. A. s. HARMON MOLTEN METAL PUMP Filed May 21, 1934 2 Sheets-Sheet 1 171 v en/ia r. wayrze. A. S. fir/"272020.

April 6, 1937.

w. A. s. HARMO'N MOLTEN METAL PUMP Filed May 21, 1934 2 Sheets-Sheet 2 Even/(3r.

wayzzafl. 5 J/Errmorq Patented Apr. 6, 1937 UNITED STATES PATENT OFFICE implication May 21,

5 Glaims.

This invention has to do with pumps for circulating molten metals or salts, for example molten lead, heated to high temperatures. Although the present pump may be regarded as t having general utility for handling fluids of this character, it has been designed particularly for circulating molten metal in oil cracking systems in which the oil is subjected to cracking by heat carried in a continuously circulated to molten metal stream.

Under the existent high temperatures and fluid condition of the molten metal at such temperatures, a major difllculty is encountered in attempting to confine the metal against leak- 15 age irom .the pump and against llow into oil lubricated bearings and other parts which should be protected against the hot metal. Accordingly, one of my principal purposes is to provide a confinement or seal that will obviate so such difllculty by insuring that the molten metal will reach only those parts oi the pump that have been purposely designed to accommodate the metal. In serving this purpose, I have provided a seal utilizing a high pressure ilxed gas 25 in such manner as to confine the flow of molten metal within predetermined limits relative to the pump bearings and other parts.

Preferably, I provide two pump shalt bearings, one lubricated by the molten metal itso sell. and the other by oil. The seal, incorporated into the pump structure between the two bearings, acts to prevent access 01 the hot metal to the oil bearing, and also to return to the pumping chamber, molten metal flowing 35 past the metal lubricated bearing. The invention also includes various features in connection with the oil feeding and discharging system lor the oil lubricated bearing, and also with reference to precautionary measures taken to prevent fire within the pump due to flashing of the lubricating oil;

All these, however, as well as additional teatures and objects or the invention will beunderstood more ully and to best advantage from the following detailed description of a typical and preierred embodiment of the invention. Pei'erence is had throughout the description to. the accompanying drawings in which:

mg. l is a general view, diagrammatic in parts, illustrating a heating system tor oil cracking units in which the present pump is used ior rculating molten metal;

the. 2 is detailed sectional enlargement oi 55 the pump:

Figs. 3 ahd i are sections on line ls' t and d e oi Fig. 2; and

Fig. 5 is a fragmentary section on line 15-45 oi a gs For the purpose of illustrating one adaptation 1934, Serial No. 328,652

WE. mil-4.11}

and use of the present type of pump, I first refer to Fig. 1 showing a heat circulating system for oil cracking plants and in which the heat carrying medium, molten metal, is circulated by my improved pump. I may state that oil conversion systems of this general character comprise the subject matter of my copending application on Oil cracking processes, Ser. No. 726,653, filed on even date herewith.

The oil cracking unit, generally indicated at 60, comprises a vertically extending shell ii containing a plurality of tubes i2 into which the cracking stock is fed through inlet 83 and distributor head I. In flowing down through the tubes, the charging stock is subjected to cracking and vaporization, the vapors flowing upwardly through the tubes counter-current to the oil streams into head I and discharging through outlet line ii. The unvaporized residuum drains into the base Ha of the shell and is discharged through line it.

Cracking tubes i2 are exterlorly heated by molten metal maintained in continuous flow through the shell ii and within a circulating system passing through a retort I! which constitutes the primary heat supply source. Retort i'l comprises a chamber l8 heated to high temperatures by combustion gases from burner i8, preheated air being supplied the burner via passage i8 and ports 20. The hot combustion gases leaving chamber i8 flow through a passage 2| leading to a heating chamber 22 surrounding the cracking unit shell II, and also through chambers 28, 24 and passage 25 joining with passage ti.

The heat transferring metal for the circulating system is initially charged into drum 26 contained within chamber 24 and exteriorly heated by the hot gases flowing to passage 25 and also to passage 2? leading from the bottom of the chamber. The molten metal pump 28 takes suction from drum 2% through line 29, and discharges the metal stream through line 30 into the retort heating coil 3! within which the metal is heated to the temperature desired (for example 1000 to 1200 R, or above) in accordance with operating conditions within the oil cracking system. The heated metal stream flows from coils 3! through line into the lower end of shell i i, thence upwardly in contact and heat transferring relation with tubes i2, and is finally discharged through outlet line 33 to be returned to drum 26. It will be noted that the lower portion of pump 28 as well as the entire remainder of the molten metal circulating system are encased within the various chambers and passages conducting hot combatstion gases from the retort. and that heat losses from the metal stream are thereby minimized and the necessary high temperatures effectively maintained. The circulation rate or gases flowing through chamber 22 is controlled by damper 22a in outlet es 221:, the damper in turn being controlled by suitable means in accordance with the molten metal temperature in line 33 leaving shell ll.

Referring now to Fig. 2, metal circulating pump 28 is shown to comprise a body 34 forming a pumping chamber 35 having an inlet 36 connecting with pump suction line 2! leading from drum 26. A pumping element, rotary impeller ll, is contained within chamber 35 and is carried on shaft 38 rotatively driven by motor 3!, the shaft extending downwardly through a chamber 40 within casing ll and through the pump body 34. The motor 38 contains the usual suspension ball bearing structure commonly adopted in line shaft impeller pumps and which serves to support the rotative parts. Any difference in expansion between the pump shaft and the pump body is taken care of by the provision of vertical clearance pockets 35a and 35b below and above the pump impeller. Leakage of the molten metal into space 35:; above the impeller, drains back through opening 31a to the pump chamber at the suction side of the impeller. It will be noted that the top and bottom clearance pockets 35a and 350 are the same diameter and that the areas on the top and bottom faces of the impeller between its outer periphery and the clearance pockets, are the same. Consequently there is established a hydraulic balance on the impeller. It may be noted that by reason of the high density of the molten metal, on starting up the pump, the impeller and shaft may float upwardly until the impeller starts pumping lead, which it does in a few revolutions, and that then the impeller and shaft return to their normal positions illustrated.

Shaft hearing it, located above pumping chamber 35 and below a gas chamber 13, is lubricated by molten metal from chamber 35 via a manifold lit leading from the pumping chamber outlet 65 and connecting through passages 48 with annular lubricantgrooves M formed within the inner faces of the bearing. Manifold M also communicates with gas chamber 43 at its lower end via passage d8. While, as will later apmar, the molten metal is maintained at some predetermined level L in the float cylinder below the upper end of bearing M, the metal will nevertheless be efiectively distributed via manifold 44 of the connecting passages throughout the hearing, by reason of the velocity head acquired by the molten metal within outlet 45 and the point of discharge into manifold 44.

The rising of molten metal within: the pump body above a predetermined level is prevented by a control system, generally indicated still, and involving the use of high pressure inert gas. The control system comprises a cylinder 5! con- 0 meeting via. pipe 52 with the lower end of gas chamber 63, and containing afloat 53 carried on rod 54 extending through guide 55. The lower end of cylinder 5! connects with the pumping chamber 35 by way of pipe 58 leading into the pump inlet line 29; A suitable inert gas is fed to drum 25 under high pressure by pump 58 through lines 51 and 59 under control of valve 6c, and to float cylinder ii and gas chamber 43 by way of lines 5i and 62.

As particularly illustrated in Figs. 1 and 2, the pump body extends vertically through the top wall W of the retort heating chamber, and is positioned relative to the wall W so that the lower portion of the pump containing the pumping chamber, as well as the lower portion of cylinder ill of the return line 56, are exposed directly to the hot gases, thereby insuring that the metal will be kept in fully heated and molten condition. The upper portion of the apparatus however, including the motor, and the hereinafter described upper oil lubricated bearing and the control apparatus for regulating the supply of inert gas to the gas chamber 43, are located above the top retort wall W outside the combustion gas zone, so that all these parts are kept at relatively low temperatures to prevent damage and deterioration by overheating.

During operation of the pump, the molten metal which lubricates bearing 42 rises through manifold 44 and the bearing itself, into the bottom of gas chamber 43. The molten metal reaching the gas chamber, immediately drains through pipe 52 into float cylinder 5|. In order to preclude the possibility of the molten metal rising within the body above drain line 52, I introduce the fixed gas to cylinder 5| and under control'of float 53, at sufficiently high pressure to keep the molten metal surface depressed to a level L below pipe 52. The admission of high pressure fixed gas to chamber 43 and cylinder 5| is regulated by valve 64 which in turn is operated through link 65 and arms 65 and 61, the latter being connected to float carrying rod 55. As the molten metal rises within cylinder 5| above level L, more gas is admitted past valve 64 to increase the pressure on the liquid surface and to depress it to the predetermined level to be maintained, and conversely as the liquid level falls.

The pump shaft extends through an oil lubricatecl bearing 68 located above the gas chamber 43, the bearing structure including a lantern gland 69 supplied with lubricant through line 70. Lubricant is also fed via line H into an annular oil groove 72 formed in the bearing surface near its lower end. In order to avoid overheating the bearing and lubricating oil, I surround the hearing 89 with a jacket 13 through which water is circulated from inlet 74 to an outlet 15. It is desirable to keep the bearing well flooded with oil, and for that reason there may be considerable oil drainage ifrom the bottom of the bearing. Accumulation of bearing oil drainage within the gas chamber is prevented by an oil slinger To keyed to the pump shaft and acting to throw the oil away from the shaft and against the body wall so that it may become trapped in annular trough H. The oil drains from the trough through pipe it into float cylinder 19, from whence it is discharged through line under control of valve 8! operatlvely connected through linkage 82 with float 83. The pump shaft is surrounded'and cooled below the oil trough ll by water circulated through jacket 84.

In order to insure that gas chamber 43 may be completely purged of air that might otherwise support combustion of oil within the chamber, I provide communicating pipes 85 and 86 through which steam or any suitable inert gas may be passed to thoroughly scavenge the chamber before the pump is started into operation. A stationary, non-rotatlve cup 81 is placed about the shaft 38 and, as shown most clearly in Fig. 5, is attached to the upper end of the pump body by bolts 81a. The lower end of the cup structure projects into the upper end of the body bore 34a and serves as a follower by means of which the packing in gland 69 may be taken up by tightenmg the nuts on bolts 81a, ample take-up clearance being provided at 81c.

Cup 81 is provided as a water receptacle for snufling any flame that might result from flashing of oil leaking upwardly from the bearing into chamber 40, it being understood that the upper portion of shaft 38 may be quite hot by reason of the high temperatures existing within and below bearing 42. Water may be circulated through .cup 81 continuously, or only when the occasion arises, by way of inlet 08 and outlet 00. both extending into chamber 40 through its bottom wall 90. The latter is secured to the annular body flange 8|.

As a further precaution against flre within chamber 40, I provide pipe connections at 92 and. 83 with shell 4| in order that steam may be passed through chamber 40 to snuff the flame if the bearing lubricant should happen to flash. The entire pump unit is supported by resting casing ll on supports M, and may be vertically 20 alined to a close degree of accuracy by adjusting screws 96 bearing against the supports.

Before starting the pump into operation and after the metal in drum 2! has become molten. gas is admittedunder pressure to the drum above 25 the liquid level via line H, and the pressure is increased until the molten metal has become elevated through line 29 into the lower portion of the pump and float cylinder ll. A valve ll is then opened to admit the inert gas into gas 30 chamber 43 of the pump and also into float cylinder I to prevent the molten metal from rising above drain connection 52 between the pump and float cylinder. Additional gas pressure is now applied to drum 2. and the molten metal is 35 elevated sumciently to completely flll the circulating system to the top of the cracking unit shell Ii. By opening vent valve 90 in line I00, gas or air may be expelled from the system as the latter fllls with the molten metal, the valve con- 40 trolled vent also serving as a means for determining when the lead has reached the high point in the system.

After the entire circulating system is fllled with molten metal, valve 9! is closed and the 45 circulating pump 28 is started into operation.

It may be observed that in shutting down the lead circuit, it is only necessary to stop the pump,

release the inert gas pressure and allow all, the

molten metal to drain back into drum 2!.

60 I claim:

l. A molten metal pump comprising a body containing a pumping chamber and a gas chamber above the pumping chamber, a rotary pumping element in said pumping chamber, a shaft connected to the pumping element and extending within the gas chamber, a shaft bearing between said. chambers and lubricated with molten metal. forced longitudinally along the shaft from the pumping chamber, a cylindercommunicating with said gas chamber and with the pumping chamber and containing a body'of molten metal fed from the gas chamber, a float in said cylinder. a high pressure gas supply line connecting with said cylinder and the gas chambenand a gas flow control valve in said line operated by said float.

2. A molten metal pump comprising a body.

containing a pumping chamber and' a gas chamber above the pumping chamber, a pumping 7o element in said pumping chamber, a motor above the gas chamber, a shaft connecting the motor with the pumping element and extending within the gas chamber, a shaft bearing between said chambers and lubricated with molten metal forced longitudinally along the shaft from the pumping chamber, an oil lubricated bearing above the gas chamber" but below the motor, means for collecting oil draining into said gas chamber from the last mentioned bearing, and a float controlled oil outlet leading from said oil collecting means.

3. A molten metal pump, comprising a body containing a pumping chamber and a gas chamber above the pumping chamber, a rotary pumping element in said pumping chamber, a shaft connected to the pumping element and extending within the gas chamber, a shaft bearing between said chambers and lubricated with molten metal forced longitudinally along the shaft from the pumping chamber, means for returning to the pumping chamber, molten metal flowing past said bearing into the gas chamber, the last mentioned means including means forming a chamber within which a body of the molten metal is maintained at a level below said gas chamber, means for communicating to both said gas chamber and to the surface of said body of molten metal, an inert gas under superatmospheric pressure, a shaft bearing above said gas chamber, means for circulating oil through the last mentioned bearing, and means in the gas chamber preventing the oil from draining down along the shaft into contact with the metal flowing upwardly through the first mentioned bearing 4. A molten metal pump comprising a body containing a pumping chamber and a gas chamber above the pumping chamber, a rotary pumping element in said pumping chamber, a shaft connected to the pumping element and extending within the gas chamber, a shaft bearing between said chambers and lubricated with molten metal forced longitudinally along the shaft from the pumping chamber, a cylinder communicating with said gas chamber and with the pumping chamber and containing a body of molten metal fed from the gas chamber, a float in said cylinder, valve means controlled by said float for admitting gas under pressure to both the cylinder and to said gas chamber, a shaft bearing above said gas chamber, means for circul'ating oil through the last mentioned bearing, and means in the gas chamber preventing the oil from draining down along the shaft into contact with the metal flowing upwgbdly through the first mentioned bearing. 3:

5. A molten metal pump comprising a body containing a pumping chamber and a gas -chamber above the pumping chamber, a motor above the gas chamber, a pumping element in said pumping chamber, a shaft connecting the motor with the pumping element and extending within the gas chamber, a shaft bearing between said chambers and lubricatedwithmolten metal forced longitudinally along the shaft from the pumping chamber, meansfor returning to the pumping chamber, molten metal flowing past said bearing into the gas chamber, a second shaft bearing above said gas chamber and below said motor, means for feeding oil to said second bearing, and means in said gas chamber preventing the oil from draining down along the shaft into contact with the metal flowing upwardly through the flrst mentioned bearing. 

